- RPG Accessory #1: Release date of October 17, 2017 with a price of $24.95
- RPG Accessory #2: Release date of September 19, 2017 with a price of $19.95
- RPG Accessory #3: Release date of July 18, 2017 with a price of $14.95
- RPG Accessory #4: Release date of June 20, 2017 with a price of $9.95
Each has the name "Untitled RPG Accessory" by Wizards RPG Team (that's the authorname all the D&D books use). They all have a noted shipping weight of 5 ounces, which suggests maybe that's a default weight (by comparison, the Player's Handbook is listed at 2.2 pounds and Volo's Guide to Monsters is 1.3 pounds). All four are listed as "Brdgm edition", which other D&D books aren't.
None of those items are the big ticket hardcovers, which tend to have a price of $49.95. Sword Coast Adventurers Guide was $39.95, and things like Dungeonology and Monsters & Heroes of the Realms were published by other companies. DM Screens and cards and similar accessories are usually handled by Gale Force 9. WotC's Mike Mearls has hinted a couple of times about a major rules expansion in the pipeline, but the latest is that "We are still deciding what form that will take" - so that sounds like its some way off yet.
What's your guess?